The present invention relates to a vehicle speed control system applied to a vehicle driven on a chassis dynamometer.
A known vehicle speed control system for a vehicle driven on a chassis dynamometer mainly by a feedback loop tends to be put in a situation that it is difficult to improve a responsibility of a vehicle speed control due to a response delay, a play and a hysteresis of the tested vehicle. In order to obtain a desired vehicle speed control result while overcoming the above situation, it was necessary for an expert engineer to perform an adjustment control using a relative long time period.
In order to solve the above-discussed weakness of the feedback controlled vehicle speed control system, Japanese Published Patent Application No. 7-325019 discloses a feed-forward control method using an inverse function MG(S)−1 of a transfer function of a tested vehicle. Further in order to solve an error generated during a period of obtaining the inverse function MG(S)−1, there is provided a vehicle model compensation control circuit so as to output a correction command for correcting an accelerator stroke command outputted from the inverse function circuit when a deviation is caused between a vehicle speed command and a vehicle speed. On the other hand, Japanese Published Patent Application No. 2003-213990 discloses another feed-forward control method arranged to compensate an error of a feed-forward control by adding a quantity corresponding to a running resistance of a tested vehicle in a feedback control circuit.